I'd have to say Path of Radiance. OMG! to see Fire Emblem in 3D and look the way it does especially the battle scenes is so cool. And it introduce the Laguz which was a very interesting and strategic unit to use. It introduced loads of new weapons and very interesting characters. King Ashnard is pure evil and the Black Knight is tough. Ike is badass in this game. He actually has a lot of speed to go with his overwhelming power. Ike is the best out of any Lord in the Fire Emblem series. And he is also in Brawl which is way awesome. Ike is older in Brawl though. It must be the form of him in Radiant Dawn. Path of Radiance is when he was still developing and there was indeed an interesting story and of course great cinematics too.

I also really loved the experience points and specified powerups that you could attach to your units throughout the game. None before did I grow an attachment towards a videogame character so strong like I did ike and his team since the first fire emblem. (If that made any sense)